To examine the within-day and between-day test-retest reliability of a testing protocol measuring the back and hip muscles fatigability using EMG median frequency

To examine the immediate and the carry-over effects of the lumbopelvic manipulation on the EMG median frequency of the lumbar multifidus (MULT), gluteus medius (GMED) and gluteus maximus (GMAX) muscles in patients with chronic low back pain (CLBP)

To compare the fatigability levels of the MULT, GMED and GMAX muscles by measuring the EMG median frequency between the participants who will receive lumbopelvic manipulation.

The research hypotheses are:

The testing protocol using EMG median frequency as a fatigue indicator for MULT,GMED and GMAX muscles will have good (ICC ≥ 0.80) within-day and between-day test-retest reliability.

The fatigability level of the MULT, GMED and GMAX muscles will significantly decrease immediately after the lumbopelvic manipulation and will be maintained over two to four days following the manipulation.

The fatigability of the MULT, GMED and GMAX muscles will significantly decrease after the intervention in the manipulation group while no change will occur in the placebo group.

Amount of Change in Muscles Endurance [ Time Frame: Baseline, Immediately, 15-minutes, 30-minutes, and two to four days after the intervention ] [ Designated as safety issue: No ]

electromyographic (EMG) median frequency will be used to determine the endurance of the gluteus maximums, gluteus medius and the lumbar multifidus muscles. The EMG median frequency will be measured in Hertz (Hz).

Secondary Outcome Measures:

Amount of Change in Pain Level [ Time Frame: Baseline, immediately, 15-minutes, 30-minutes, and two to four days after the intervention ] [ Designated as safety issue: No ]

Pain Visual Analogue Scale (VAS) will be used in this study. Participants will be asked to rate their pain level on a 10-cm horizontal line which is marked on the left end "No pain" and on the right end "Extreme pain". Then, the pain level for a specific participant will be determined by measuring the line from the "No pain" end to the mark placed by the participant.

Each participant will be asked to lie in a supine position. The treating investigator will stand on the opposite side of the low back pain. Then, the participant will be asked to clasp his/her hand behind the neck. The treating investigator will side bend the participant's spine towards the non-painful side. The treating investigator will reach through the participant's hands and perform a spinal rotation away from the painful side. The treating investigator's other hand will be placed over the anterior superior iliac spine (ASIS) of the painful side. Lastly, the treating investigator will take up the slack and maintain the pressure on the ASIS for 5-10 seconds and ask the participant whether he/she can tolerate the pressure. If the participant can tolerate the pressure for at least 5 seconds. Then, the subjects will be re-positioned to the starting position.

Each participant will be asked to lie in a supine position. The treating investigator will stand on the opposite side of the low back pain. Then, the participant will be asked to clasp his/her hand behind the neck. The treating investigator will side bend the participant's spine towards the non-painful side. The treating investigator will reach through the participant's hands and perform a spinal rotation away from the painful side. The treating investigator's other hand will be placed over the anterior superior iliac spine (ASIS) of the painful side. Lastly, the treating investigator will take up the slack and maintain the pressure on the ASIS for 5-10 seconds and ask the participant whether he/she can tolerate the pressure. If the participant can tolerate the pressure for at least 5 seconds, a verbal permission will be obtained from the participant and then the treating investigator will proceed and apply a high-velocity low-amplitude posterior thrust force over the ASIS.

Other: Lumbopelvic Manipulation

Each participant will be asked to lie in a supine position. The treating investigator will stand on the opposite side of the low back pain. Then, the participant will be asked to clasp his/her hand behind the neck. The treating investigator will side bend the participant's spine towards the non-painful side. The treating investigator will reach through the participant's hands and perform a spinal rotation away from the painful side. The treating investigator's other hand will be placed over the anterior superior iliac spine (ASIS) of the painful side. Lastly, the treating investigator will take up the slack and maintain the pressure on the ASIS for 5-10 seconds and ask the participant whether he/she can tolerate the pressure. If the participant can tolerate the pressure for at least 5 seconds, a verbal permission will be obtained from the participant and then the treating investigator will proceed and apply a high-velocity low-amplitude posterior thrust force over the ASIS.

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Please refer to this study by its ClinicalTrials.gov identifier: NCT01861418